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Coming home Sunday from our 1300 mile trip on I-35 near Hillsboro TX I noticed the bus voltage gauge start climbing, 13.5, 14.2 14.8, 15.2, then to 16 volts. I pulled over and measured the alternator output with my digital meter and it was 16 volts. I pulled the belt off and used the genny to charge the bus batteries through the Trace for the last 4 hours of the trip.

I went out today and rehooked everything and the voltage is back to normal 13.9-14.2. The only thing I can say is that when it went cuckoo it was raining really hard on the trip and things were really wet back in the engine room. You think that is what caused it? What else should I check? I'd hate to get out on the road and have it do it again. I'm glad I keep a constant scan on my gauges. That would have boiled out my starter batteries really quick. This is a Neihoff 350 amp alternator with a strap on OEM voltage regulator.

David, unless you have an exceptionally high DC load (like running an A/C thru the inverter) you could easily go 4 hours without needing to charge the bus batteries. Just watch the DC voltage and do not let it go much below 12 volts. I drove from Phoenix to LA one time without an alternator with no problem.

Coming home Sunday from our 1300 mile trip on I-35 near Hillsboro TX I noticed the bus voltage gauge start climbing, 13.5, 14.2 14.8, 15.2, then to 16 volts. I pulled over and measured the alternator output with my digital meter and it was 16 volts. I pulled the belt off and used the genny to charge the bus batteries through the Trace for the last 4 hours of the trip.

I went out today and rehooked everything and the voltage is back to normal 13.9-14.2. The only thing I can say is that when it went cuckoo it was raining really hard on the trip and things were really wet back in the engine room. You think that is what caused it? What else should I check? I'd hate to get out on the road and have it do it again. I'm glad I keep a constant scan on my gauges. That would have boiled out my starter batteries really quick. This is a Neihoff 350 amp alternator with a strap on OEM voltage regulator.

David

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Life should NOT be a journey to the grave with the intention of arriving safely in an attractive and well preserved body. But rather to skid in sideways, chocolate in one hand, a good Reisling in the other, body thoroughly used up, totally worn out and screaming: WOO HOO, what a ride

Sounds to me like your regulator is the culprit, or its connections. Its the regulator that tells the alt what to put out. If the wire that goes to the regulator has a poor connection (increased reisistance) the regulator might only be seeing a lower voltage and keep telling the alt to produce more. I'd definitely check it all, or have an electrical shop check it all.

Good for you for catching that, you saved your batteries.

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Jim StewartEl Cajon, Ca. (San Diego area)

Travel is more than the seeing of sights, it is a change that goes on, deep and permanent, in the ideas of living.

I would suspect the voltage regulator may have had a water short that stopped when it dried out. Personally, I would replace the regulator (since the alternator seems to be running alright). When I replaced the Delco 50DN gear drive alternator in my bus, I also replaced the voltage regulator, even though the old one seemed to be alright. The old regulator was transistorized and about the size of a dozen egg carton, maybe minus two eggs. The new one is digital and the size of 1 1/2 decks of cards. Also the new one is much better at regulation so the headlights don't flicker up and down nearly as much. If you do replace your regulator, make sure that all the connectors are tight and away from any kind of ground. My regulator is actually in the right rear of the interior, right at the rear engine firewall. You might consider mounting the regulator inside also. Then that will for sure eliminate the possibility of getting both wet and hot with the engine heat. Good Luck, TomC

Same as Brian. Got mine from C&J. I did have to run a new wire direct from the battery to the regulator, though, as it was not regulating well when connected into the old wiring. Too much resistance someplace was causing the regulator to fluctuate. Running the wire direct from the battery made it rock stable!

A word of caution. I did the same thing but had to run the hot wire from a DC source that was hot when the ignition switch was turned on. Otherwise, there was a continuous drain on the battery which would discharge them in a couple of days. Richard

Same as Brian. Got mine from C&J. I did have to run a new wire direct from the battery to the regulator, though, as it was not regulating well when connected into the old wiring. Too much resistance someplace was causing the regulator to fluctuate. Running the wire direct from the battery made it rock stable!

Logged

Life should NOT be a journey to the grave with the intention of arriving safely in an attractive and well preserved body. But rather to skid in sideways, chocolate in one hand, a good Reisling in the other, body thoroughly used up, totally worn out and screaming: WOO HOO, what a ride

A word of caution. I did the same thing but had to run the hot wire from a DC source that was hot when the ignition switch was turned on. Otherwise, there was a continuous drain on the battery which would discharge them in a couple of days. Richard

Yeah, now that you mentioned it, there was an ignition connection on the regulator, which the old one didn't have. It came with a jumper bar that could be used to tie the sense and ign terminals together, if the sense was switched. I think I attached the old wiring to the ign as it is switched by the main power switch (I think there's a relay in the circuit), and was then able to run the sense wire direct to the batteries, and didn't use the jumper bar. If anyone needs more detailed information on this, let me know and I'll go decipher the thing. I haven't looked at it since I installed it last July, and it's been working perfectly.

I called a Neihoff dealer and described the symptoms. He thinks it got wet, somehow. Since it is normal now he recommended a watchful eye. A new regulator is $330. A new alternator is $3500. These things are very expensive. I don't think I could by an off the shelf regulator given the special OEM cannon plug on this one. If I did I would have to get help from you guys about the wiring. It only has 4 wires from the regulator. It seems if the correct connections were made an OEM regulator woulldn't be required.

David, the critical part in replacing a regulator is determining the characteristics of the alternator field. You need to know what the nominal excitation voltage and amps are and then you need to know the input power requirements. With that you can replace it with an off the shelf Basler or similar type regulator.Richard

I called a Neihoff dealer and described the symptoms. He thinks it got wet, somehow. Since it is normal now he recommended a watchful eye. A new regulator is $330. A new alternator is $3500. These things are very expensive. I don't think I could by an off the shelf regulator given the special OEM cannon plug on this one. If I did I would have to get help from you guys about the wiring. It only has 4 wires from the regulator. It seems if the correct connections were made an OEM regulator woulldn't be required.

David

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Life should NOT be a journey to the grave with the intention of arriving safely in an attractive and well preserved body. But rather to skid in sideways, chocolate in one hand, a good Reisling in the other, body thoroughly used up, totally worn out and screaming: WOO HOO, what a ride

Those pieces of information should be available from the alternator manufacturer or from the regulator manufacturer, if there is no information on the units themselves. Otherwise it would be very difficult to obtain that information. Richard

Being very alternator challenged, how would I determine these parameters? My tools are limited to a digital tester and not much else.

David

Logged

Life should NOT be a journey to the grave with the intention of arriving safely in an attractive and well preserved body. But rather to skid in sideways, chocolate in one hand, a good Reisling in the other, body thoroughly used up, totally worn out and screaming: WOO HOO, what a ride